1. Field of the Invention
The present invention relates to an apparatus used for preventing plasma etching, and particularly to an apparatus for preventing plasma etching of a wafer clamp in semiconductor fabrication processes.
2. Description of the Prior Art
The fabrication process of semiconductor devices on the semiconductor wafer typically requires the deposition of multiple metal, dielectric, and semiconductor film layers on the surface of a semiconductor wafer. The film layers are typically deposited onto the semiconductor wafer in vacuum chambers. Certain processing operations require the deposition of film layers or the etching of a previously deposited film layer. During these processing steps, one must properly align and secure the wafer in the process chamber in which the desired deposition or etch process is performed.
Generally, the semiconductor wafer is supported in the process chamber. The semiconductor wafer is placed on, and secured to, the upper surface of the wafer clamp prior to the deposition or etch process. FIG. 1 shows a cross-sectional view of a process chamber. The pedestal 10 is supported, having a wafer support surface, in the process chamber. The bottom electrode 15 is positioned on the pedestal 10. The semiconductor wafer 25 is placed on the bottom electrode 15, the semiconductor wafer 25 secured to a wafer clamp 20, using high pressure gas through a gas hole 55 to generate a high vacuum pressure, thereby securing the semiconductor wafer 25. The quartz ring 30 is positioned on the wafer clamp 20. The top electrode structure 50 is placed, including a top electrode 35, a cooling plate 40, and an anode 45, adjacent the quartz ring 30.
FIGS. 2A and 2B are a partial sectional view of the apparatus of FIG. 1, respectively showing a top view and a bottom view of a traditional wafer clamp. The wafer clamp 140 comprises a clamp ring 100, a planar holder 110, a concave holder 120, and a depression 130. The clamp ring 100 includes a tapered surface to receive the semiconductor wafer. The planar holder 110 is placed adjacent the depression 130. The depression 130 is higher position adjacent the planar holder 110. The concave holder 120 is positioned in the planar holder 110.
FIG. 3 is a partial sectional view of the apparatus of FIG. 1, showing a bottom view of a traditional wafer clamp deposited polymer. The polymer 150 is formed, an approximately circular ring having protected function surrounding the clamp ring 180, in the deposition or etching process. However, a portion of the polymer 150 is merely formed on backside of the concave holder. Then the polymer 150 is not formed on the backside of the planar holder. The backside of the planar holder will be etched for plasma to form a etched region 160. Due to the wafer clamp 170 is etched. The wafer clamp 170 will be reduced the lifetime of usage. Thus, this present invention is disclosed by applying novel clamp wafer structure, and improving the disadvantage.